minecraft latest snapshot says the command /modifyitem command does not exist in game
also i don't know if this is a bug are not but in the latest snapshot it seems to rain none stop
thats about it.
Comments 2
See here for information: https://www.reddit.com/user/Dinnerbone/comments/6wjeai/possible_new_113_command_modifyitem/
This command isn't final or even implemented.
the /modifyitem command hasn't been coded yet. They said it will be in a future snapshot